Water heater control system



p 1942- c. M. OSTERHELD 7,016

WATER HEATER CONTROL SYSTEM Filed May 19, 1941 I L M,

(EIVVENQ 'JR. C1 /"f 135 T5 1TH E 1.33

Patented Sept. 29, 1942 UNITED STATES PATENT OFFICE WATER HEATER CONTROL SYSTEM Clark M. Osterheld, Stoughton, Wis, assignor to McGraw Electric Company, Elgin, 111., a corporation of Delaware Application May 19, 1941, No. 394,229

7 Claims. (Cl. 219-49) My invention relates to electric control systems thereshown generally only a water tank. ii and particularly to water heater control systems. which may be relatively smaller than the ordi-- An object of my invention is to provide a thernary hot water tank installed in homes and mostatic control means associated with a hot which may have associated therewith an electric water tank that will reduce the number of cycles 6 heater II which is so designed and constructed of heatin as to have a higher wattage capacity than the Another object of my invention is to provide heaters ordinarily used in such installations. For thermal means for controlling the energization illustrative purposes only, I may use a twenty of the heater of a hot water tank that will permit gallon or thirty gallontank instead of a forty or of withdrawing a relatively large amount of hot 10 a sixty gallon tank and I may use a 3009 watt or water from the tank, when substantially all of even larger electric heater instead of a 1060 watt the water has been heated and the heater has or a. 1500 watt heater. As hereinbefore stated,

been deenergized, before the heater is reenerthese figures are illustrative only and are not to glzed, be considered as limiting my invention.

Other objects of my invention will either be The usual cold water inlet pipe and hot water apparent from a description of one form of sysoutlet pipe, heat insulation and supporting means tem and device embodying my invention or will for the tank H are to be consi ed. being be pointed out in the course of such description vided but as they constitute no part of my ln'velland set forth in the appended claims. tion they are not shown. in detail in the drawing. In the single sheet of drawings: A pair of supply circuit conductors i5 and I! Figure 1 is a diagrammatic view of a system may be connected with the incoming supply of heater control embodying my invention as apcult conductors connected to the generating plied to a hot water tank, and. equipment at the central station. Supply cir uit Fig. 2 is a vertical sectional view taken through conductor l5 may be connected to e. fixed contact the thermal control means shown generally only member 59 or to a substantially rind contact arm in Fig. 1 ot the drawing. is of a thermal switch 2!, which mimics a sec It is sometimes found advantageous, by central end contact arm, 23 ingly stations supplying current to relatively large into engagement with the subsi ntially rigid urban and suburban territories, to provide a rela- 0 contact arm l9. While Fig. i of the drawing tively small hot water storage tank having assonot show the support or mounting for the switch, elated therewith a single electric heater of relathis forms no part of my invention and col tively'high wattage. One of the attendant phases supporting means are to be considered as of economy obtained by the use of a relatively provided. Contact arm 23 is connected by a sm ll st r se nk is n only in the first cost conductor 25 with one terminal or the heater is, of the installation but also the lower heat radiatthe other terminal of which is connected to the ing surface and therefore the smaller degree of other supply circuit conductor ll.

heat radiation and attendant temperature drop I provide a thermally a'ctuabie controller or the hot water in case the tank is full of hot signated generally by numeral 27 and shown water which is not being used. schematically only in Fig. l of the drawing but 22 One of the attendant disadvantages of using a have illustrated one form of such device c l sin le therm l he ter control switch s ject bodying invention or. an scale it.

either'to the temperature of the tank at one 2 of the drawing. given point or subject to the temperature of the I provide a good heat conducting water in the tank at one given point is that if the which may, for mate; :2, made of heater and its associated thermal control switch which is or substanti L-shane are mounted in or on the tank adjacent the shorter 3i and a anger l lower end thereof, the open thermal heater conarm 33 is adapted to ez nrl trol switch will be caused to reclose in case a in the wall of tank relatively small amount of hot water is with r, and held in such pe drawn from the tank, thereby causing a relaalter described. The a tively large number of heating cycles in case of bore therein to withdrawals of small quantities 61' hot water a heat cond from the tank, with attendant radio interierbrass and whz ence. w in the opening Referring first to Fig. 1 of the drawing, I have tubular member to his the I vs?" 1 end which yent such reclosure provided with an annular collar 4! which .1,

adapted to fit into the inner end of a bushing opening and closing of the heater control switch which will, of course, be found effective to reduce radio interference in the case where a radio instrument is operating at the time of making and breaking the engagement between the thermal heater control switch contacts.

Various modifications may be made in the system embodying my invention as herein shown and described and allisuchmodifications clearly ,coming within the scope of, the'appended claims are to be considered as being covered thereby.

I claim as my invention:

1. In a water heating system for a hot water l3 which is adapted to have screw threaded engagement with an opening 45 in the tank wall H. A lock nut 41 may have screw threaded en-f d d d onlyiwhioh points are spaced vertically from each gagement with the'outer end portion of arm"33 so that when nut ll-gs screwed tightly up against the outer end of bushing 53, the annular collar ill will be moved intoclose engagement-withthe correspondingly shaped inner end of to obtaina fluid-tight, joint. v V

expansion rod Jill is adapted'to .be held in an opening 5! extending from the outer end of arm 38 to substantially the junction of, arms 33 and 3!. I may providea small bore 53 in'the central portion of member 29 to receive the inner end of expansion rod 59 and I'may provide a. bushing 55 immediately adjacentand inside of the outer end of arm 33 pansion rod ifi in the bore 5i.

While I have mentioned thatthe-member '29 may be made of brass, I do not desire to be lim-' ited thereto since it may be made of other metals or alloys and I may make theexpansion rod 39 of aluminum or a high expansion brass. The tubular member 37 is preferably made of a metal or of an' alloy having, a relatively high thermal resistance to the transmission of heat and I may make member 39 of a material such as brass which will receive and conduct the heat of the ambient water. u i

Let it be assumed that the heater 3 had been energized for a sufiicient length of time to cause all or substantially all of the water in the tank to have become hot with the result that the expansion of rod as to the position shownin Fig. l of the drawing caused deenergization of the heater 93. If, new, a small amount of hot water, say

bushing 5 3 only a few quarts, is needed and is withdrawn.

it is possibletha't the level of the incoming cold water, entering at the bottom of thetank, would be below member 39 but above say the'upper end ofarrnii.

The design, construction and adjustment of the assembly 27 is S lchthat even thouglithe expansion rod 8% and'partlcularly its surrounding mem-, bers were subject to cold water, it would not contract s'u'ficiently to cause reengagement of con tact arm 23 with contact arm i9 becaus of the to properlysupport extank having anelectric heater, a heater control switch and thermally-actuable means responsiyejlto-{tank-Iwater temperature at two points other to cause closure of said switch and energization 'ofthe heater only after the withdrawal of enough hot water from the tank to cause the upper level of the entering cold water at the bottomv of the tank to reach substantially the upper one of'said two points. r i V 2.- In a water heating system fora hot'water tank having an electric heater, a heater control switch and thermally-actuable means responsive to tank water temperature at two points only, which points are spaced vertically from each-other to cause opening of said switch and deenergization of the heater only after the lower level zof thebhot water, as the-water is being heated,- reaches substantially the'lower one of said two points.

3.;In a water heating system for a'hot water tank having an electric heater, a heater control switch and thermally-responsive means inside fact that heat conducting rod 35 was sun cone ducting enough heat from therhot water surroundingthe upper end of the assembly 27 to pre- I d of the thermal'control switch for the heater. f 7

Only when additional water, say to the extent of several gallons, is withdrawn from the tank so that the entire assembly 2? is subject to cold water, will the expansion rod 59 contract enough,

to cause engagement of contact arm 23 with con tact arm 5 9 and reen'e rgization of the heater i3.

It therefore, evident that the device ei'nbodying my invention provides a relatively simple thermally actuable assembly of elements having high heat conductivity toprevent, frequent the tank engaged .by the "water and responsive to water temperature at two points only which points are spaced vertically apart an appreciable distance to cause energization of the heater only after the withdrawal of such an amount of hot water from the tank aswill cause the upper level of the entering cold water at the bottom of the tank to reach substantially the upper' one of said two points.

4. In a water heating system for a hot water tank having an electric heater, a heater control switch and thermally-responsive means 'for actuating said switch comprising an expansion I rod extending into the tank, an enclosing means for saiclrodoi' high thermal conductivity at two points only, which point-scare spaced apart vertically an appreciable distance and engaged by the water I; in a the the withdrawal of such a quantity of hot water fromthe tank as will cause the upper level of the cold water entering the tankto reach the upper of said two points; i 7

5. 1m a water heating system for a hot water tank-having an electric heater, a heater-control switch and thermally-responsive means for actuating said switch comprising an expansion rod extending into the tank,an enclosing means for said rod: of high thermal conductivity at points are spaced apart two points only, which vertically an appreciable distanceand engaged by the water inithe tank, said thennally-respon sive means being adapted to cause opening of said switch and deenergizaticn of the heater only after the lower levelof thehot water,

water is being heated, reaches substantiallythe lowerone of said two points.

6. In a water heating system for a hot water I tank, said thermally-responsive meansbe'ing adapted to cause closure of said" switch and energization of "the heater only after as the tank having a single electric heater adjacent its lower end, a heater control switch and thermally-actuatable means responsive to tank water temperature at two points only, which points are near the lower end of the tank and are spaced vertically from each other to cause energization of the electric heater only after the withdrawal of enough hot water from the tank to cause the upper level of the entering cold water at the bottom of the tank to reach substantially the upper one of said two points.

7. In a water heating system for a hot water tank having a single electric heater adjacent its lower end, a heater control switch and thermally-actuable means responsive to tank water temperature at two points only, which points are near the lower end of the tank and are spaced vertically from each other to cause energization of the electric heater only after the withdrawal of enough hot water from the tank to cause the upper level of the entering cold water at the bottom of the tank to reach substantially the upper one of said two points and to CLARK M. OSTERHELD. 

